The first European to navigate the St. Lawrence was Jacques Cartier, who on 9 June1534 first sighted the river and also claimed New France for Francis I. Until the early 1600s, the French used the name Rivière du Canada to designate the Saint Lawrence upstream to Montreal and the Ottawa River after Montreal. The Saint Lawrence River served as the main route for exploration of the North American interior from Europe.

The St. Lawrence was formerly continuously navigable only as far as Montreal due to the Lachine Rapids. The Lachine Canal was the first to allow ships to pass the rapids; the Saint Lawrence Seaway, an extensive system of canals and locks, now permits ocean-going vessels to pass all the way to Lake Superior.

Names

A note on translation: Occasionally, the French name fleuve Saint-Laurent is wrongly translated as Saint Lawrence Seaway, on the idea that it uses the word fleuve, not rivière. However, the word fleuve simply means a river that runs to the sea, and is appropriately translated by river. The seaway is a system of artificial canals, and is called in French voie maritime du Saint-Laurent.

The source of the North River in the Mesabi Range in Minnesota is considered to be the source of the Saint Lawrence River. Because it crosses so many lakes, the Saint Lawrence River frequently changes its name. From source to mouth, the names are: